Hi Salim, Buzz here. Well, i don' t use a ladder. We get a maint. lift, drive under the center engine and raise the platform.
There are access hatches in the bottom. On the DC-10 you could unlatch and unfold a patio, complete with seats along each side. Of course it was generally oily up there, normally windy at most airports. And everything you sat on, stepped on , or grabbed was generally covered with non-skid paint, haerd on the skin. So you'd better wear gloves, boots, long sleeve coveralls.
We wouldn't have to do much between flights, but on the last flight of the day we'd add oil and check the CSD for the generator.
The 727 is similar, but you get a small wave of oil sloshing out when you open the cowling..... if you didn't want to open the little oil access door.
g'day